1. Field of the Invention
The present invention relates to an insulating film forming composition, more specifically to a composition capable of forming an insulating film to be used in electronic devices and the like and good in film properties such as dielectric constant and mechanical strength. The invention also pertains to a forming process of the insulating film and an electronic device having the insulating film.
2. Description of the Related Art
In recent years, with the progress of high integration, multifunction and high performance in the field of electronic materials, circuit resistance and condenser capacity between interconnects have increased and have caused an increase in electric power consumption and delay time. Particularly, the increase in delay time becomes a large factor for reducing the signal speed of devices and generating crosstalk. Reduction of parasitic resistance and parasitic capacity are therefore required in order to reduce this delay time, thereby attaining speed-up of devices. As one of concrete measures for reducing this parasitic capacity, an attempt has been made to cover the periphery of an interconnect with a low dielectric interlayer insulating film. The interlayer insulating film is expected to have excellent heat resistance in a thin film formation step when a printed circuit board is manufactured or in post steps such as chip connection and pin attachment and also chemical resistance sufficient to withstand the wet process. In addition, a low resistance Cu interconnect has been introduced in recent years instead of an A1 interconnect, and along with this, CMP (chemical mechanical polishing) has been employed commonly for planarization. Accordingly, an insulating film having mechanical strength great enough to withstand this CMP is required.
Highly heat-resistant interlayer insulating films such as polybenzoxazole, polyimide, polyarylene(ether) and the like have been disclosed for long years. Materials having a lower dielectric constant further are demanded in order to realize a high speed device. Introduction of a hetero atom such as oxygen, nitrogen or sulfur or an aromatic hydrocarbon unit into the molecule of a polymer as in the above-described materials, however, increases a dielectric constant owing to high molar polarization, causes a time-dependent increase in the dielectric constant owing to moisture absorption, or causes a trouble impairing reliability of an electronic device so that these materials need improvement.
Compared with a polymer composed of a hetero-atom-containing unit or aromatic hydrocarbon unit, a polymer composed of a saturated hydrocarbon has a smaller molar polarization so that it has advantageously a lower dielectric constant. However, a hydrocarbon such as polyethylene having high flexibility has insufficient heat resistance and therefore cannot be used for electronic devices.
Polymers having, in the molecule thereof, a saturated hydrocarbon having a rigid cage structure such as adamantane or diamantane are disclosed (EP1605016A2). Adamantane or diamantane is a preferable unit because it has a diamondoid structure and exhibits high heat resistance and low dielectric constant.